Thermostat



Nov. 27, 1962 G. F. DALES 3,066,206

THERMOSTAT Filed Feb. 9, 1959 INVENTOR. 5 GEORGE FRANKLIN DALES u 20 BY Z United States Patent 3,066,206 THERMOSTAT George Franklin Dales, 253 Castle Blvd, Akron, ()hio Filed Feb. 9, 1959, Ser. No. 791,952 4 Claims. (Cl. 209-138) This invention relates to a thermostat of the type made of a small plastic or metal tube which usually measures no more than one-quarter or three-eighth inch in diameter, and no more than an inch or two in length.

In the thermostat of this invention there is a bimetal electrode and an electrode made of spring metal which presses against or lies adjacent the inside of the Wall of the casing of the thermostat. Contact between the two electrodes is made between contact buttons located on the electrodes.

In the past, in the manufacture of various types of such small thermostats it has been customary to locate one contact button (herein called the first button) in the casing of the thermostat and have the casing live, i.e. have it carry a current. The bimetallic electrode is located within the casing and is insulated from it. Contacts are made and broken between a contact button on the bimetallic electrode (herein called the second button) and the first button. Contact buttons are usually made of silver, and the casing is made of aluminum, steel, or other metal than silver. Whatever the metal of the button and whatever the metal of the casing, two dilferent metals are required. These different metals have different electrical potentials and when located adjacent one another as they are in the prior art casing, electrical currents flow between them. This causes rapid decomposition of the more positive metal at the juncture of the two.

In the thermostat of this invention, the first button is not located in the casing but is located on a spring metal electrode, and the portion of this electrode on which the button is located is pressed against the inner surface of the casing. This electrode may or may not be insulated from the casing.

The thermostat is calibrated by bending the end which holds the bimetallic electrode, thereby increasing or decreasing the temperature at which this electrode makes and breaks contact with the first button. The pressure of the spring electrode against the casing must be suflicient to press that portion of the electrode on which the first button is located, against the casing regardless of how the end of the thermostat is bent during its calibration. Unless this electrode is elastic and bears against the inner surface of the casing, it may be separated from the casing during calibration, making uncertain the temperature at which the thermostat is operative. By using a spring metal as the electrode and having the electrode at all times in pressure contact with the inner surface of the casing, the position of the contact button within the thermostat is constant regardless of how the end of the thermostat is bent during calibration.

The invention will be further described in connection with the accompanying drawings, in which- FIG. 1 is a section through a thermostat in which the spring electrode is insulated from the casing;

FIG. 2 is a section through a thermostat in which the spring metal is not insulated from the casing;

FIG. 3 is a section on the line 33 across the thermostat shown in FIG. 1;

FIG. 4 is a detail showing in section a modification of the thermostat shown in FIGS. 1 and 3; and

FIG. 5 is a detail showing in section a modification of the thermostat shown in FIG. 2.

The casing 1 of the thermostat is made from a tube of aluminum or other heat-conductive material. One end ICC is closed by squeezing the top 2 and bottom 23 into contact.

The electrodes 5 and 6 are held in the other end of the thermostat encased in insulation 7 which may be glass fiber or Teflon or other resin, or other suitable material.-

The insulation is preferably somewhat plastic so that there is no danger of injuring it when the end of the thermostat is bent during calibration. The top 9 and bottom 10 of this end of the thermostat are flattened against the insulation. The top and bottom are staked at 12 so that to calibrate, the end projecting beyond the stakes can be readily flexed. As it is flexed, the contact button 15 on the bimetallic electrode 6 is moved toward or away from the contact button 16' on the spring electrode 5.

The spring electrode 5 is made of beryllium or other spring metal or alloy. It may be the nickel-base alloy known as Inconel which contains approximately 13 percent of chromium, 6 percent of iron, and small amounts of manganese, silicon and copper. Any good spring conductor can be used. Before insertion in the thermostat, the distance between the ends of the electrodes 5 and 6 is much greater than within the thermostat so that when they are put in the thermostat the portion of the spring electrode on which the button is located is held under tension against the inner surface of the thermostat.

The bimetallic electrode may be located in either of two positions. Thus, the contact buttons 15 and 16 are closed either when the thermostat cools down to a certain temperature, or when it is raised to a certain temperature.

As the temperature of the bimetallic electrode is changed sutficiently for the button 15 to contact the button 16, the contact is made; as the buttons separate the contact is broken. The spring electrode is always pressed against the inner surface of the thermostat and its position is unchanged by calibration of the thermostat. Thus, the temperature at which the contact is made and broken is as constant as though the button were held in the casing.

The advantage of this structure, including a spring electrode, is that the casing itself is a continuous tube, and the contact button is entirely separate from it and located inside of the thermostat, so that there is no corrosion of the casing as when the button is in the casing.

The inner surface of the casing is insulated by a lacquer 17 and the surface of the spring element which contacts the casing is similarly insulated by lacquer 18. Any other suitable insulation may be used. It is not necessary to insulate both the casing and the electrode. Thus both electrodes may be insulated from the casing.

Alternatively, when the spring element is insulated from the casing, the bimetallic element may be in contact with the casing.

FIGURE 2 shows a similar structure in which a bimetallic electrode 20 makes and breaks contact with the spring electrode 22, but the insulation 25 at the end of the electrode insulates only the bimetallic electrode from the casing. The spring element 22 is in conductive contact with the casing, and as in the construction shown in FIG. 1, this electrode is always in pressure contact with the casing.

Although generally the calibration is effected by bending the staked end of the thermostat, a screw may be provided for fine adjustment. FIGURE 4 shows such a screw 30 threaded into the case 1 of a thermostat such as shown in FIGS. 1 and 2. This is preferably an insulating screw made of porcelain or other insulating material. The drawing shows the screw as passing through a hole in the insulating coating 17 and bearing against the insulation 18.

In FIG. 5, which shows a modification of the thermostat shown in FIG. 2, the spring element 22 is not insulated aoeaaee from the casing. The screw 35 may be a metal screw. It bears directly against the spring element 2.2.

If the bimetallic element of the thermostats shown in the drawings bends toward the spring element as the temperature drops, the temperature at which the thermostat circuit is closed, actuating heating means, is raised by turning the adjusting screw and thereby moving the spring element toward the bimetallic element. Converly, if the thermostat is arranged so that a rise in temperature causes the bimetallic element to bend toward the spring element, the temperature at which the thermostat circuit is closed and actuates cooling means is lowered by turning the adjusting screw and moving the spring element toward the bimetallic element.

Modifications in the structure shown and, more particularly described, may be made. For instance, the casing may be made from a tube of conductive organic plastic, instead of metal. The insulation may be of thermosetting composition. Other modifications will suggest themselves to the man skilled in the art. is covered in the claims which follow.

What I claim is:

1. A thermostat which includes a heat-conductive casing with a bimetallic element and a spring electrode therein adapted to make and break contact adjacent one of their ends as the temperature of the bimetallic element is changed, the other end of said bimetallic element and spring electrode being held in one end of the casing which is adapted to be bent for calibration of the thermostat, with a major portion of the area of one surface of the portion of the spring electrode which is within the casing sprung into contact with the inner surface of the casing The invention i and adapted to remain in such contact as said end of the casing is bent in calibration of-the thermostat.

2. The thermostat of claim 1 in which the casing is electrically conductive, the spring electrode is insulated from the casing in said end thereof in which it is held, and said surface of the spring electrode is electrically insulated from the casing.

3. The thermostat of claim 1 in which the inner end of an adjustment screw threaded through the casing bears against the spring electrode near said end which is adapted to make and break contact with the bimetallic element.

4. The thermostat of claim 1 in which the casing is electrically conductive, the spring electrode is in conductive contact with the casing in said end of the casing and said surface of the spring electrode is sprung into conducting contact with the inner surface of the casing.

References Cited in the file of this patent UNITED STATES PATENTS 2,331,425 Russell Oct. 12, 1943 2,497,397 Dales Feb. 14, 1950 2,538,476 Smith Jan. 16, 1951 2,743,335 Moyer Apr. 24, 1956 2,820,870 Moksu Ian. 21, 1958 2,835,767 Graf et a1 May 20, 1958 2,855,485 Webking Oct. 7, 1958 2,925,483 Wells Feb. 16 1960 2,925,599 Wells Feb. 16, .1960

FOREIGN PATENTS 1,023,116 Germany Jan. 23, 1958 

